Lubricant proportioning pumps are used, for example, for controlled lubrication of an internal combustion engine power plant. Such known lubricant proportioning pumps employed for this purpose are constantly supplied with lubricant during operation at a rate representing the rate of consumption plus an excess. Out of this available volume, inside the pump, lubricant is withdrawn and delivered according to the speed of the engine, the rate of delivery of lubricant being influenced as well by the load setting of the engine controls. In accordance with the requirements of the engine, the added effect of the load setting has the result that at a high load, the delivery piston executes its full stroke, thus increasing the flow of lubricant, and at low load, for example when idling, with correspondingly shorter stroke of the delivery piston, a lesser flow of lubricant is delivered. But this means that after starting and while warming up, when the engine load is low, and especially at low temperatures, the lesser flow of lubricant supplied to the engine may possibly fail to adequately lubricate, with premature wear of the power plant as the likely consequence.